THE KIDNEYS SECRETION OF URINE. 517 



in large doses, was not found to produce any decided change in the acidity 

 of the urine; the only perceptible effect being a slight diminution of the de- 

 crease which takes place after taking food, and a slight augmentation of the 

 increase after fasting. On the other hand, the use of liquor potnssa; iu large 

 doses lessens the acidity of the urine, preventing it from rising after fasting 

 to the height it would otherwise attain, and increasing its alkalescence after 

 a meal ; but it does not render the urine by any means constantly alkaline, 

 nor does it hinder the variations produced by the state of the stomach from 

 being very evident. Tartaric acid in large doses temporarily increases the 

 acidity of the urine, causing it to rise considerably higher than usual after a 

 fast, but not preventing that which is passed a few hours after food from 

 becoming alkaline. Tartrate of potash in large doses, on the other hand, 

 has a marked effect in rendering the urine alkalescent ; still, it does not pre- 

 vent the usual recurrence of the acidity some hours after a meal. The Urine 

 of Herbivorous animals is almost invariably alkaline; partly because their 

 food contains a large quantit} 7 of alkaline and earthy bases, in combination 

 witli citric, tartaric, oxalic, and other acids, which are decomposed within 

 the system ; and partly because the amount of sulphuric and phosphoric 

 acids, generated as products of the oxidation of the elements of the tissues 

 or of the surplus food, is not sufficient to neutralize them. Such is the con- 

 dition which occasions the alkalinity of Human Urine, when a portion of the 

 acid which would otherwise show a predominance is directed into another 

 channel ; and it is exaggerated in those states, in which, either from the irri- 

 tating nature of the food, or from the irritable condition of the stomach, an 

 undue quantity of acid is poured out into that viscus ; so that, its reaction 

 being habitually acid, that of the urine becomes habitually alkaline. Such 

 a state of the urine must be carefully distinguished, as Dr. Beuce Jones has 

 pointed out, 1 from that in which the alkalescence is clue to the presence of 

 volatile, and not to that of fixed alkali ; the difference being easily recogniz- 

 able by the influence of the liquid upon reddened litmus-paper, for the res- 

 toration of its blue color is permanent in the latter case, but only transitory 

 in the former. The alkalescence due to the presence of volatile alkali is due 

 to the decomposition of urea, whilst the urine is yet within the bladder, 

 through the agency of morbid secretions of that viscus ; and it disappears 

 when this organ returns to its healthy state. On the other hand, the alka- 

 lescence from fixed alkali proceeds from disordered action of the stomach, 

 which is usually connected with disorder of the general system ; and it per- 

 sists until this can be remedied. In both forms of alkalescence, there is a 

 precipitation of earthy phosphates ; but in the alkalescence from fixed alkali, 

 the precipitate usually consists almost entirely of phosphate of lime ; whilst 

 in that from volatile alkali, the amorphous sediment of phosphate of lime 

 is mingled with prismatic crystals of the phosphate of ammonia and mag- 

 nesia. These precipitates may be obtained from healthy urine, by adding to 

 it a solution of potash or of ammonia; and the decomposition of such urine, 

 which begins to take place very soon after it leaves the body, gives rise to 

 the same precipitation, by the production of carbonate of ammonia at the 

 expense of its urea. 



416. Thus, then, we have seen that the Kidneys serve as the special in- 

 struments for depurating the Blood of those highly-azotized compounds, 

 which are formed in the system by the decomposition of the materials of the 

 albuminous and gelatinous tissues, and also by that of the non-assimilated 

 components of the food. We have seen also, that they serve for the removal 

 of certain excremeutitious compounds, of which carbon is a principal in- 



1 Medical Times, Dec. 13th, 1851. 



